Farm Ireland
Independent.ie

Saturday 26 May 2018

Winning the battle against skin allergens in horses

While some irritations can be difficult to identify, most can be overcome with a combination of good management, observation and control

Ringworm is the most common skin irritation in horse herds in this country.
Ringworm is the most common skin irritation in horse herds in this country.
Ringworm
Siobhan English

Siobhan English

During this year's show circuit, dozens of horse owners have been discussing the issue of skin irritations caused by summer flies, midges and ringworm.

At this stage in the summer, there are few yards in the country which have escaped from some form of skin irritation among their horse herds, with several owners reporting that horses have broken out in bizarre sores just days before a major show, resulting in withdrawal.

While the root of some skin irritations can be difficult to identify, ringworm continues to be one of the most prevalent, identifiable and treatable skin diseases in horses.

Ringworm

Despite its name, Ringworm has nothing to do with worms and is in fact caused by a fungal infection.

It is transmitted among horses by direct contact with an infected animal such as a cat (one of the main carriers) or humans, or by indirect contact via contaminated tack, or fungal spores within the environment.

Illness, poor nutrition, overcrowding, age and stressful environments predispose horses to infection. Continuous wetting of the horse's skin, such as sweating, washing-down can decrease the skin's protective barrier, therefore enabling infection to occur.

The classic ringworm lesion is a circular patch of hair loss with stubbly hairs on the margin. The skin can appear to be crusted and/or scaly. Ringworm lesions usually begin as small raised lumps that progress to the typical ringworm lesion. The areas commonly affected are the face, neck and girth area and horses can become itchy and may also show evidence of pain.

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Ringworm is usually a self-limiting disease and most horses recover quickly with a treatment such as Imaverol, which is an effective wash also suitable for the treatment of other fungal infections.

"This summer we have seen a lot of cases of ringworm and we are testing for it every day using mostly skin scrapings," said Tom Buckley, head of microbiology at the Irish Equine Centre. "At least 30pc to 40pc of what we test comes back as positive for ringworm.

"In many of the cases, we look for an allergen, as it can be anything from grasses to soya in their feed."

The Irish Equine Centre uses the services of Spanish company, Alergovet, who has the facilities to test for up to 50 allergens in horses. These include various types of grasses, weeds, trees, moulds and mites that can cause hives. Midges, meanwhile, can be one of the key causes of sweet itch.

Sweet itch

Found more commonly in half-breds than thoroughbreds, sweet itch rears its ugly head here in Ireland in the summer months owing to the large presence of midges.

After being exposed to the allergen (saliva from the midge bite), allergic horses will develop a 'type 1' hypersensitivity reaction, resulting in histamine being produced by the body's immune system, exactly the same as happens to people who suffer from hay fever. This is an over-reaction to the bite, resulting in swelling and intense itching of the skin.

Just like with people suffering an allergic skin reaction, the desire to itch and rub at the affected site is intense. Consequently, the horse will start to rub and chew at the area, which can then become infected, making the problem even worse. The more often that a horse is bitten by midges, the worse the reaction becomes.

Once it starts in an animal, sweet itch is incurable, but it can be managed using all-over flysheets, stabling your horse from 4pm-8am during the summer months and using effective creams such as Summer Freedom Salve in conjunction with highly-potent fly repellent sprays such as Super Plus.

Shapleys Original MTG is widely used for a variety of skin problems, including sweet itch and is also said to be most effective in the promotion of hair regrowth.

A natural effective way of warding off midges and flies is the use of garlic in a horse's feed, although this must be used in moderation as over-use can equally cause an adverse reaction.

Mange

Mange is caused by microscopic mites that invade the skin of otherwise healthy animals. The mites cause irritation of the skin and a hypersensitivity reaction, resulting in itching, hair loss and inflammation.

Sarcoptic mange (scabies, body mange)

Although rare, sarcoptic mange is the most severe type of mange in horses. The first sign of mange is intense itching, which is caused by hypersensitivity to mite saliva and feces.

For this, most vets will administer fast-acting injectable antihistamines and, if needed, low doses of steroids.

Chorioptic mange (leg mange)

Leg mange tends to occur in heavy breeds of horses. Signs start as itching affecting the legs (most often the hind legs) around the foot and fetlock. Raised bumps are seen first, followed by hair loss, crusting, and thickening of the skin.

The signs lessen in summer but return with cold weather. The disease persists without treatment, but usually clears when treated. Topical treatments recommended for other types of mange are usually effective.

Straw itch mites (forage mites)

Straw itch mites usually feed on organic material in straw and grain but can infest the skin of horses. Raised bumps and hives appear on the face and neck if horses are fed from a hay rack, and on the muzzle and legs if fed from the ground. Again, itching is variable and can be controlled with medication.

Rain scald

Owing to Ireland's inclement weather, rain scald can often be an issue in the summer as well as winter months. It is a bacterial infection which multiplies rapidly in a moist environment.

Starting off as raised bumps mostly on the shoulders and hindquarters, it can be easily cured by removing the horse from wet conditions and treating them with disinfectant rinses to prevent further infection.

Lice

Both chewing lice (feed on dead skin cells) and sucking lice (feed on blood) can infect horses, causing skin irritation and itching. Hair loss usually starts on the shoulders and neck, as well as on the head and the base of the mane and tail. Affected areas may also have abrasions and scabs from rubbing and possibly secondary infections.

Flattened insects up to two to four millimeters long may be visible if the hair is parted and the skin examined in good light. Pale, translucent eggs may be attached to nearby hairs. Lice infestations tend to be more severe during the winter months but can occur at any time of year.

Several types of treatment products are available over the counter, including Dermoline Insecticidal Shampoo and Dermoline Stable Louse Power.

Any skin ailment, disease or allergen that causes discomfort to horses is equally frustrating to owners, but in the end, it all comes down to good horse management, observation and control.

COMMON ALLERGENS IN HORSES

Grasses

Grass Mix I (Ryegrass, Timothy, Cocksfoot, Bluegrass, Festuca)

Grass Mix II (Scutchgrass, Bentgrass, Wheatgrass, Velvetgrass)

Grass Mix III (Zeae, Wheat, Avenagrass, Barley, Rye)

Weeds

Plantain

Mugwort

Fat hen

Dandelion

Nettle

Daisy

Rape

Russian Thistle

Trees

Pine

Privet

Cypress

Plane

Poplar

Oak

Beech

Elm

Mimosa

Ash

Lime

False Acacia

Willow

Mites

Dust mite

Flour mite

Storage mite

Mould mite

Moulds

Alternaria alternate

Aspergillus

Penicillium notatum

Cladoporium herbarum

Rhizopus nigricans

Fusarium solani

Food allergens

Wheat

Rye

Barley

Oat

Maize

Alfalfa

Insect allergens

Culicoides

Cadiss fly

Fly

Mosquito

Black fly

Horse fly

Tested by Alergovet

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